Fix OAuth callback route to match Nextcloud redirect URI

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

routes/web.php

@@ -8,4 +8,4 @@ Route::get('/', function () {
 });
 
 Route::get('/oauth/redirect', [OAuthController::class, 'redirect'])->name('auth.nextcloud');
-Route::get('/oauth/callback', [OAuthController::class, 'callback'])->name('auth.nextcloud.callback');
+Route::get('/auth/nextcloud/callback', [OAuthController::class, 'callback'])->name('auth.nextcloud.callback');